Hi,
The language variant Serbian (Latin, Serbia and Montenegro (Former)) seems to have disappeared from Studio. The language variant does, however, seem to be mentioned in the supported languages list (http://producthelp.sdl.com/SDL_TRADOS_STUDIO_2015/CLIENT_EN/introducing/inintroducingsdltradosstudiosupportedlanguages.htm).
Does this depend on OS or .NET version?
Regards,
Lennart